The invention relates to a trench cover for temporarily covering a trench made in a footpath or roadway.
Digging trenches for laying cables, pipes and the like is extremely labour intensive. There are severe constraints on efficient digging because of the need to complete the digging, fitting and filling operation as quickly as possible. This is especially difficult in situations where the path or roadway must be kept open. Thus, a considerable amount of work is required to backfill trenches while the trench digging work is ongoing. Regularly, a large proportion of the available working day is involved in temporary backfilling and the renewal of the backfilling to allow the work to continue. This is a major cost factor as not only is their a high labour content but also backfill is generally a waste product that cannot be used as permanent trench filling.
Various attempts have been made to provide a trench cover to temporarily cover a trench. Such trench covers however have a number of disadvantages and are consequently used infrequently, backfilling being the preferred option.
U.S. Pat. No. 4,801,483 describes a ground opening cover with anchoring holes for anchoring the cover in place. It is not practical to temporarily cover a trench with such plates as each plate must be anchored separately and each of these anchors must be released to remove the cover.
GB-A-2305954 describes a temporary trench cover comprising an upper plate with depending walls for inserting into the trench. An angle piece is secured to one depending wall to provide a connection means in the form of a channel having an upwardly opening mouth into which an opposite depending wall of an adjacent plate is engaged. While such an arrangement prevents longitudinal movement between adjacent cover plates the plates are easily removed by pulling the plates upwardly using the finger receiving apertures. Thus, the plates are not secured against unauthorised removal. In addition, the arrangement does not facilitate covering of a trench which is not straight.
EP-A-0431777 describes a cover for temporarily covering a trench which is releasably engagable with an adjacent cover. The cover is a tight fit in a trench and the arrangement does not facilitate relative movement between adjacent cover elements. Further, unauthorised removal is not prevented as the covers can be relatively easily removed by moving a cover out of the general plan of the assembly.
GB-A-2 321 486 describes a temporary trench cover comprising a hollow shell of plastics material with a downwardly protruding portion to define lateral abutment faces which are spaced apart by a width corresponding to the width of the trench so as to engage the side walls of the trench. The cover may have a part-circular tongue at one end for engaging in a corresponding part-circular recess defined by an open-ended socket of an adjacent element to allow adjacent cover elements to be articulated. Such an arrangement is difficult to manufacture and, the covers can be relatively easily removed by unauthorised personnel by moving a cover out of the general plan of the assembly. In addition, while the arrangement illustrates relative movement between adjacent covers the gaps between adjacent covers presents a hazard as, for example, a bicycle wheel may become wedged in the gap with attendant safety problems.
This invention is therefore directed towards providing an improved trench cover which will overcome at least some of these problems.
According to the invention there is provided temporary trench cover element comprising a cover member for extending over a trench, the cover member comprising a pair of ground engaging portions bridged by a central trench covering portion, the ground engaging portions defining a pair of opposite sides for location outside of a trench and the cover member having a pair of transverse ends extending transversely between the opposite sides, confinement means extending downwardly from the central portion of the cover member to confine the cover with respect to a trench opening and interlink means comprising a first interlink means at one transverse end and a complementary second interlink means at an opposite transverse end, one of the first or second interlink means being engagable underneath the other of the first and second interlink means of a like cover element on assembly, a cover element being relatively movable with respect to an adjacent cover element to follow the contour of a trench.
In a preferred embodiment of the invention one of the interlink means is oversize with respect to the other of the interlink means to allow limited relative movement between the interlink means so that the cover elements follow the contour of the ground.
Preferably wherein the interlink means of adjacent cover elements are relatively moveable in a vertical direction and/or a horizontal direction to follow the vertical contour of the trench.
In one embodiment of the invention the first interlink means comprises a head part projecting from a transverse end of a cover member and the second interlink means comprises a slot adjacent a transverse end of a cover member to receive the head part of a first interlink means of an adjacent like cover element on assembly.
Preferably, in one embodiment the second interlink means comprises a slot defined in an underside of the cover member. In a preferred embodiment the slot is a downwardly opening slot and the head part engages in the slot from below. Ideally the slot is oversize with respect to the head part to allow limited relative movement between the head part and the slot so that a cover element may be moved relative to an adjacent cover element to follow the contour of a trench. In one arrangement the slot is defined in an underside of the central portion of the cover member.
In a particularly preferred embodiment of the invention the interlink means includes at least one wing which extends from a transverse end of the cover member. Most preferably the at least one wing extends for a distance to bridge at least portion of a gap between adjacent cover elements, on assembly.
Ideally the cover member has a wing receiving recess to receive portion of the end wing of an adjacent cover element, on assembly.
The end wing is preferably located to one side of one or both of the interlink means. Preferably there are two transversely spaced-apart end wings. In one embodiment the first interlink means is a slot at a first transverse end of the cover and the or each wing extends from the first transverse end.
Most preferably the or each end wing extends from one cover element underneath an adjacent cover element, on assembly.
In a particularly preferred embodiment at least one transverse end is shaped to facilitate limited relative movement between end marginal edges of adjacent cover elements. Ideally at least one end marginal edge is at least partially of curvilinear shape, preferably of arcuate shape, ideally of generally convex shape.
In another embodiment of the invention the first interlink means comprises a male part projecting from one transverse end and the second interlink means comprises a slot adjacent the opposite transverse end for receiving the head part of an adjacent like cover element, on assembly, the head part and slot being shaped to facilitate assembly of the head part into the slot in a first orientation of the cover element and to prevent removal of the head part from the slot in another, assembled orientation.
In this case preferably the male part has a projecting head section and a neck section of reduced width with respect to the head section. Ideally the slot has a top entry opening to permit entry of the head section in the first orientation and to prevent exit of the head part in the assembled orientation. Preferably the slot includes a side assembly opening through which the neck section of the male part extends in the assembled orientation.
In one embodiment of the invention the cover element includes handle lifting means.
Ideally the cover member has an anti-slip surface.
In one embodiment the cover element includes tracking code means. Preferably the code means is housed within the cover member.
In another embodiment the cover element includes anchoring means for anchoring the cover member. The anchoring means may include an anchor formation such as a slot or hole in or on the cover member. The anchor formation may be a slot for receiving an anchoring clip.
Preferably, for ease of handling and use the cover element is from 200 mm to 500 mm long, preferably either from 200 to 300 mm long, or from 300 to 400 mm long.
The invention also provides a cover assembly comprising a number of cover elements as of the invention.